The invention relates to a measurement device having a cable probe, and to a method for shortening the cable of a cable probe.
Various embodiments of measurement devices having cable probes are known, which normally comprise a housing in which measurement device electronics are accommodated, and to which a probe is fitted which is in the form of a cable, a bar or rod. For example, a capacitive measurement device is known from level measurement, in which at least one electrode (which is used for measurement) of the measurement capacitor is in the form of a cable or rod which is immersed in the medium to be measured. In a further measurement device for level measurement, electromagnetic pulses, for example, are transmitted on a waveguide, which is in the form of a rod or cable and is immersed in the medium to be measured, to the surface of the medium. A hydrostatic measurement device is also used for level measurement, in which a pressure sensor is mounted at the end of a cable and is lowered into the medium to be measured. All these probes which are in the form of cables, bars or rods and are connected to a measurement device, are referred to for the sake of simplicity, in the following text by the term xe2x80x9ccable probesxe2x80x9d. The bars, rods or cables are accordingly referred to, for the sake of simplicity, as xe2x80x9ccablesxe2x80x9d.
The measurement devices having cable probes are normally mounted on a container which contains the medium to be measured, with the housing frequently being mounted in or on a container wall such that the cable probe projects into the interior of the container, and into the medium. The cable probes are either themselves electrically conductive, or have at least one electrical conductor in the interior, in the sense of electrical wires. The cables or the electrical conductors are normally connected to measurement device electronics in which the measurement signals are produced and processed. The measurement device electronics are in turn normally connected to an instrument or switching console or to some other higher-level unit, where the level measurements are processed.
A common feature of all these cable probes is that their length depends on the medium level expected or to be measured. If the cable probe needs to be shortened in response to changed measurement conditions, then, normally, the shortening of the cable and its processing, in particular its mounting, are problematic and difficult to carry out. A special tool is often required for this purpose, so that, in many cases, the work can be carried out only at the manufacturer""s premises or supplier of the measurement device. Furthermore, with various devices, the electrical connection of the cable probe to the measurement device electronics is linked to the mechanical mounting of the cable in such a way that the cable probe cannot be shortened in a simple manner.
One object of the invention is thus to provide a measurement device having a cable probe, and a method according to which the cable probe can be shortened in a simple manner by an end user, to be precise if possible on site and without needing to use any special tools or other manufacturer-specific tools.
This object is achieved according to the invention by a measurement device
having a device housing which accommodates measurement device electronics,
having a cable probe mounted therein,
which comprises a built-in sleeve provided in the interior of the device housing,
which built-in sleeve can be fitted in or removed from the interior of the device housing by rotation about its longitudinal axis
and whose operating position is fixed by at least one detachable mounting.
One advantageous embodiment of the invention provides that the cable probe comprises a cable which is mounted in the built-in sleeve by means of a clamping cone which surrounds the cable.
In a further advantageous embodiment, the built-in sleeve is surrounded by a connecting sleeve of the device housing.
In another particularly advantageous embodiment of the measurement device according to the invention, the built-in housing has a mounting collar by means of which the built-in sleeve is mounted in its operating position in the device housing by means of a number of screws.
Even further embodiments of the invention provide that electrical conductors, which are located in the interior of the cable of the cable probe and are passed out in the built-in sleeve, are connected to a plug and/or to a plug connecting socket, in which the plug or the plug socket can be accommodated by the built-in sleeve.
Further advantageous embodiments of the measurement device according to the invention relate to a seal in an internal area of the connecting sleeve from a medium to be measured by means of a conical seal which is located in the interior of the connecting sleeve and surrounds the cable.
In other special embodiments of the invention, further seals are used in order to seal a part of the device housing which accommodates the measurement device electronics from an internal area of the connecting sleeve which accommodates the cable probe, and/or from an internal area of the built-in sleeve.
Furthermore, the invention achieves the object by means of a method for shortening a cable, which is mounted in a device housing of a measurement device, of a cable probe, comprising the following method steps:
a) after opening the device housing, the measurement device electronics are removed;
b) electrical connections between the measurement device electronics and the cable probe are interrupted;
c) releasing a built-in sleeve mounted on the housing side, which built-in sleeve surrounds the cable as a result of which at least one seal which surrounds the cable and acts with respect to the medium to be measured, is relieved of load in a connecting sleeve which also surrounds the cable of the cable probe;
d) the built-in sleeve is drawn out of the device housing, together with the cable and the seal;
e) the cable is shortened by a desired length;
f) a seal, a built-in sleeve and clamping cone are once again drawn over the remaining cable of the cable probe, and the cable is mounted in the built-in sleeve, by pulling it into said built-in sleeve;
g) the electrical connections between the cable probe and the measurement device electronics are made once again;
h) once the measurement device electronics have been fitted, the device housing is closed once again.
One particular advantage of the invention is that the only tools which are required to shorten the cable probe are a conventional screwdriver, pliers for cutting through and cutting off the cable of the cable probe, and/or a cutting tool like to a blade for exposing the electrical conductors contained therein.
A further advantage of the invention is that the cable of the cable probe can be shortened without the housing of the measurement device needing to be removed from a container which contains the medium to be measured.
The invention will be described and explained in the following text using an exemplary embodiment and with reference to the attached drawing. Identical features and parts of the various embodiments of the invention are provided with the same reference symbols, for simplicity. In the figures: